These patented inserts have three start threads that act as a tripod when starting, which helps them remain in line with the hole as they are driven. With three threads, they have a faster feed rate than standard inserts. The head has a collar that is about 2mm wider than the typical pre-drill hole, so they seal as they seat. They are available with M6, M8, 1/4-20 or 5/16-18 internal threads, and with an overall length of 15mm or 18mm. All are zinc-plated steel. Made in Germany.